The present invention is directed to a multi-span bridge support system for vehicles with high braking forces, such as vehicles which are moved at least partially magnetically.
The requirements for an elevated roadway with magnetic rails are different in substantial areas from the requirements for conventional track systems. Where magnetic rails are used, the vehicle and the roadway represent a coupled oscillation system in which determined natural frequencies and stiffnesses are required after extensive examination and testing of the roadway. Accordingly, the superstructure forming the elevated roadway must have great bending stiffness with regard to vertical forces and transversely directed horizontal forces along with a great torsion stiffness. Moreover, the vehicle poses great demand on the alignment and level of the working surfaces in the roadway, that is, the stator plates, the lateral guide rails and the sliding rails. A particular problem results from the starting and the braking forces which are non-uniform relative to the rails and must be safely conducted into the supports as longitudinally directed horizontal forces.
Therefore, the primary object of the present invention is to provide a statically effective, constructionally simple and economical arrangement for the construction and support of the superstructure for a roadway for vehicles with high braking forces, particularly for vehicles moving along magnetic rails.
In accordance with the present invention, the superstructure for a multi-span bridge support system of the type mentioned above includes a row of end-to-end single-span prestressed concrete girders with torsionally stiff cross-sections. The single-span girders are supported on a row of support columns spaced apart in the elongated direction of the girders. The single span girders are provided with upwardly extending girder webs with the roadway slab supported on and being cantilevered outwardly from the girder webs. At least two adjacent single-span girders are supported at adjacent ends so as to be fixed and at the opposite ends so as to be horizontally movable. The opposite ends of the girders are supported on the support columns. The fixed ends of the girders are supported on the common support column and form a fixed point. At the fixed supports there is at least one vertical bearing for transmitting horizontally directed forces acting in the long direction of the girders and positioned in a notched region in the lower part of the girders whereby the notched region has a vertical surface and a horizontal surface juxtaposed to a corresponding vertical surface and horizontal surface on the common support column. Tension members extending perpendicularly to the surfaces supporting the vertical bearings extend through the vertical bearing joints and are secured to the girders on the opposite sides of the joint. At the fixed point there is at least one horizontal bearing for transmitting vertical loads from the notched region of the girder into the top of the support column.
The tension members extend at least approximately on the axis of the vertical bearings, that is, the axis of the horizontal forces being transmitted. Preferably, the tension members are anchored in the transverse cross-girders at the adjacent ends of the girders.
The invention has a substantial advantage in that a pair of vertical bearings are provided at the opposite sides of the support column forming the fixed point. The vertical bearings are secured in the notched region in the lower part of the girders with a vertical bearing on each of the opposite sides of the support column. The vertical bearings are arranged so that the tension members positively pressurize the bearings within the cross-sectional region of the girders. The transverse cross-girders at the ends of the single span girders located above the notched region can be cantilevered outwardly from the cross-section of the elongated girder so that the bearings arranged at the ends of the girders for transmitting vertical loads are arranged so that one-sided lifting of the girders does not present a problem even when high transversely directed horizontal forces are encountered.
The arrangement and position of the vertical and horizontal bearings offers the possibility that the tension members required for the positive pressurizing of the vertical bearings, are continuous along the entire length of the adjacent girders without any bonding action between the tension members and the girders and support column. In other words, the tension members can be anchored at the opposite ends of the girders from the ends located at the fixed point. Since the tension members are continuous at one or both sides of the column support forming the fixed point without any bonding action with the girders, an additional single-span girder can be supported for horizontal displaceability with vertical bearings being arranged between the additional girder and one of the other girders for transmitting the forces produced by the tension members extending through the girders. By post-tensioning or releasing the tension force acting on the tension members, a simple arrangement is afforded for regulating the bending of the girders and for levelling the upper edges of the girders forming the roadway.
To achieve continuous effect of the single-span girders, that is, to produce negative bending moments at the support columns, tension members extending through the joint and the end cross girders at right angles and without any binding action can be provided at the fixed point of the support in the upper region of the girders. These upper tension rods are preferably tensioned against at least one vertical bearing positioned in the upper part of the joint between the girders.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention .